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Switched to inverse storage of the interrupt flag so as to reduce logical burden when storing IRQ line history.

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This commit is contained in:
Thomas Harte 2016-10-28 20:52:43 -04:00
parent b64ae904a5
commit 613b5b3f98
1 changed files with 23 additions and 23 deletions
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46
Processors/6502/CPU6502.hpp
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@ -143,7 +143,7 @@ template <class T> class Processor {
*/
RegisterPair _pc, _lastOperationPC;
uint8_t _a, _x, _y, _s;
uint8_t _carryFlag, _negativeResult, _zeroResult, _decimalFlag, _overflowFlag, _interruptFlag;
uint8_t _carryFlag, _negativeResult, _zeroResult, _decimalFlag, _overflowFlag, _inverseInterruptFlag;
/*
Temporary state for the micro programs.
@ -191,7 +191,7 @@ template <class T> class Processor {
*/
uint8_t get_flags()
{
return _carryFlag | _overflowFlag | _interruptFlag | (_negativeResult & 0x80) | (_zeroResult ? 0 : Flag::Zero) | Flag::Always | _decimalFlag;
return _carryFlag | _overflowFlag | (_inverseInterruptFlag ^ Flag::Interrupt) | (_negativeResult & 0x80) | (_zeroResult ? 0 : Flag::Zero) | Flag::Always | _decimalFlag;
}
/*!
@ -203,12 +203,12 @@ template <class T> class Processor {
*/
void set_flags(uint8_t flags)
{
_carryFlag = flags & Flag::Carry;
_negativeResult = flags & Flag::Sign;
_zeroResult = (~flags) & Flag::Zero;
_overflowFlag = flags & Flag::Overflow;
_interruptFlag = flags & Flag::Interrupt;
_decimalFlag = flags & Flag::Decimal;
_carryFlag = flags & Flag::Carry;
_negativeResult = flags & Flag::Sign;
_zeroResult = (~flags) & Flag::Zero;
_overflowFlag = flags & Flag::Overflow;
_inverseInterruptFlag = (~flags) & Flag::Interrupt;
_decimalFlag = flags & Flag::Decimal;
}
/*!
@ -461,7 +461,7 @@ template <class T> class Processor {
enum InterruptRequestFlags: uint8_t {
Reset = 0x80,
IRQ = 0x40,
IRQ = Flag::Interrupt,
NMI = 0x20,
PowerOn = 0x10,
@ -471,7 +471,7 @@ template <class T> class Processor {
bool _ready_is_active;
bool _ready_line_is_enabled;
bool _irq_line_is_enabled, _irq_request_history;
uint8_t _irq_line, _irq_request_history;
bool _nmi_line_is_enabled, _set_overflow_line_is_enabled;
/*!
@ -547,11 +547,11 @@ template <class T> class Processor {
_ready_line_is_enabled(false),
_ready_is_active(false),
_scheduledPrograms{nullptr, nullptr, nullptr, nullptr},
_interruptFlag(Flag::Interrupt),
_inverseInterruptFlag(Flag::Interrupt),
_s(0),
_nextBusOperation(BusOperation::None),
_interrupt_requests(InterruptRequestFlags::PowerOn),
_irq_line_is_enabled(false),
_irq_line(0),
_nmi_line_is_enabled(false),
_set_overflow_line_is_enabled(false)
{
@ -617,8 +617,8 @@ template <class T> class Processor {
}
#define bus_access() \
_interrupt_requests = (_interrupt_requests & ~InterruptRequestFlags::IRQ) | (_irq_request_history ? InterruptRequestFlags::IRQ : 0); \
_irq_request_history = _irq_line_is_enabled && !_interruptFlag; \
_interrupt_requests = (_interrupt_requests & ~InterruptRequestFlags::IRQ) | _irq_request_history; \
_irq_request_history = _irq_line & _inverseInterruptFlag; \
number_of_cycles -= static_cast<T *>(this)->perform_bus_operation(nextBusOperation, busAddress, busValue); \
nextBusOperation = BusOperation::None;
@ -720,7 +720,7 @@ template <class T> class Processor {
case OperationRSTPickVector: nextAddress.full = 0xfffc; continue;
case CycleReadVectorLow: read_mem(_pc.bytes.low, nextAddress.full); break;
case CycleReadVectorHigh: read_mem(_pc.bytes.high, nextAddress.full+1); break;
case OperationSetI: _interruptFlag = Flag::Interrupt; continue;
case OperationSetI: _inverseInterruptFlag = 0; continue;
case CyclePullPCL: _s++; read_mem(_pc.bytes.low, _s | 0x100); break;
case CyclePullPCH: _s++; read_mem(_pc.bytes.high, _s | 0x100); break;
@ -925,14 +925,14 @@ template <class T> class Processor {
case OperationDecrementOperand: _operand--; continue;
case OperationIncrementOperand: _operand++; continue;
case OperationCLC: _carryFlag = 0; continue;
case OperationCLI: _interruptFlag = 0; continue;
case OperationCLV: _overflowFlag = 0; continue;
case OperationCLD: _decimalFlag = 0; continue;
case OperationCLC: _carryFlag = 0; continue;
case OperationCLI: _inverseInterruptFlag = Flag::Interrupt; continue;
case OperationCLV: _overflowFlag = 0; continue;
case OperationCLD: _decimalFlag = 0; continue;
case OperationSEC: _carryFlag = Flag::Carry; continue;
case OperationSEI: _interruptFlag = Flag::Interrupt; continue;
case OperationSED: _decimalFlag = Flag::Decimal; continue;
case OperationSEC: _carryFlag = Flag::Carry; continue;
case OperationSEI: _inverseInterruptFlag = 0; continue;
case OperationSED: _decimalFlag = Flag::Decimal; continue;
case OperationINC: _operand++; _negativeResult = _zeroResult = _operand; continue;
case OperationDEC: _operand--; _negativeResult = _zeroResult = _operand; continue;
@ -1247,7 +1247,7 @@ template <class T> class Processor {
*/
inline void set_irq_line(bool active)
{
_irq_line_is_enabled = active;
_irq_line = active ? Flag::Interrupt : 0;
}
/*!